A wireless device may be capable of communicating over a network using one or more defined data transfer specifications. For example, a wireless device may support an Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, a European Telecommunications Standards Institute (ETSI) specification, and/or another wireless-based standard or specification. For example, a particular ETSI specification is Enhanced General Packet Radio Service (EGPRS), also known as Enhanced Data rates for Global Evolution (EDGE). EGPRS is a specification for data transfer on Global System for Mobile communications (GSM) and Time Division Multiple Access (TDMA) networks.
In an acknowledged mode of operation, a minimal communication protocol between a transmitter and a receiver may include: 1) an encoded data block sent from the transmitter to the receiver; and 2) an acknowledgment (ACK) or no acknowledgement (NACK) message sent from the receiver to the transmitter, which indicates whether the encoded block was received and decoded correctly. Some data transfer specification versions anticipate an ACK or NACK after each sent data block. Other versions may support transmission of data blocks with selective acknowledgement. The communication protocol between the transmitter and the receiver may include other control messages, as well (e.g., Release, Link Control, etc.). For purposes of brevity, these additional messages are not described in detail herein.
Either way, if the transmitter does not receive an ACK within a particular time interval, the transmitter may assume that the receiver did not receive or decode one or more data blocks correctly. In this case, or when the transmitter receives a NACK message, the transmitter may retransmit the data block. In the presence of a noisy channel, retransmissions may be frequent, which may effectively reduce the data transfer rate.